Imperial v Metric Measures

Please could we BAN any further discussion about metric v Imperial units. It's boring and wastes everyone's time.

I remember reading many years ago an old woodworking magazine where it stated "use 1-1/2 pairs for heavy doors.

Cannot remember the magazine name but always remembered that quote.

regards

Centimetres belong with dressmakers and schoolteachers. Engineers use metres and millimetres. Similarly radius is a concept used by mathematics teachers and turners. Engineers use diameter, —— Discuss.

Dave……tongue in cheek!

Or maybe not! The USA has two definitions of the foot. PatJ refers to the common one, which is the International Foot, but the US also has a Survey Foot, used in mapping and to define land ownership. Although the difference is tiny, it often causes problems, and the US is dumping the Survey Foot in favour of the International Foot (defined as 0.3048 metres) at the end of this year. Although most of the population won't notice, it's an important change to those who need it, and long overdue. Many of those to whom survey measure matters were in favour of metricating, but resistance to change was too strong.

When it comes to assessing measurement systems it's extremely unwise for individuals to rely on a narrow work experience. A major flaw of the Imperial System is it creates pockets of illusion that nothing is wrong. Within narrow confines all seems well - building sites and engineering workshops do their own thing. Unfortunately, problems appear like a cockroach infestation when worlds meet. In WW2 the small difference between the US and British Inches caused endless compatibility problems : stuff that should have fitted together, didn't. Today, trade is global, and the metric system is almost universal - countries see more value adopting an international system rather than sticking to traditional measure no-one else understands. Non-standard products are a pain.

One fault of the Imperial System is it's full of conversions. 12 inches = 1 foot, 3 feet = 1 yard, 14 pounds = 1 stone, 1760 yards = 1 mile, etc etc. Another, it's internally incoherent, causing unnecessary disjoints between - for example - electrical and mechanical measure. (Power: one Horse Power is 550 foot pounds per second, with no obvious connection with Watts. Sums involving power are easier in metric, because the relationship between mass, length, and time is consistent within the metric system.)

Imperial is often slightly easier for basic niche work, but the metric system pulls away as complexity increases, and is universal. There's no difference between Building Site and Rocket Science.

Much worse in the past. We benefit from an Imperial System that's been massively tidied and simplified. Nonetheless, it's still not logical or internally consistent, and this causes grief as soon as anything complicated is tackled. Men with tape measures and micrometers aren't doing anything complicated, so Imperial seems all good to them. Scientists were first to dump Imperial in favour of a rationally designed system, and mathematical engineers soon adopted it too.

The main problem with metric is getting everyone on board. The English speaking world is full of objects defined in Imperial measure, that don't convert to metric in nice round numbers - window frames! So switching from Imperial to Metric is painful.

Countries that ruthlessly switched as fast as possible suffered much less pain than countries like the US and UK who chose to spread the agony over many decades.

In my opinion allowing a major technical improvement to be delayed by small-c conservatives wanting to buy potatoes in lbs was a serious failure of leadership. Buying spuds in kilograms might be a minor temporary discomfort until people get used to it, but lumbering designers with clunky mathematics and forcing British industry to try and sell Imperial machines to Metric customers damaged the national interest. And despite the advantage of a gigantic home market, US industry is also finding failure to metricate is a liability.

That large numbers of people are comfy with a wonky system is no reason to perpetuate it. If it's broke, engineers fix it. And they don't refuse to fix stuff because their little bit seems OK!

Dave

I'll be honest, I'll happily switch between units depending on specifications, drawings or materials and to me 10' is about 2" over 3m. I have no problem with railways being measured in chains, within the railway industry it is an established and internally consistent unit and any attempt to change it would almost certainly be expensive and prone to (potentially catastrophic) errors during the transition period. On the other hand, I had no hope of guessing how long 2,300' is whilst 700m or 35 cricket pitches (chains) is easy to picture.

I fail to see why anybody would consider the imperial/customary system simpler or more natural. To switch from mm to m to km is just a matter of moving the decimal 3 places between units, whilst to go from inches to feet, to yards chains, furlongs and miles requires a number of sometimes complex divisions.

Consider the difference in gauge between the Iberian railways 5' 5 21/32" and the rest of Europe's 4' 8 1/2" standard gauge. To convert in imperial/US customary units it is necessary to either carry out calculations in three different units and somehow merge them together or convert everything to the lowest common denominator. In the metric system it is just a matter of 1.668 - 1.435. An engineer designing variable gauge wheelsets would find it far easier in metric than adding the further complication of converting the final 5/32" to thou.

Brian G

I think Martin hits the nail on the head.

I should say "Everybody around these parts.....".

I have heard that many outside the US can look at metric dimensions and immediately know that 7,426 mm is something they can envision. I suppose it is like learning a language (math is just a foreign language really), the language you learn first becomes the one that seems natural.

We did a couple of German steel plant designs in the mid-south, and we all had to get German dictionaries and learn German, in order to read the machine drawings, plus all the German drawings were in metric, so all that had to be converted.

We just don't build stuff in metric here, and people don't generally think in metric either, at least not in the building trade. They tried to convert us in school, but it never took off.

Inches/feet/yards/miles is just too convenient in the building/industrial construction market.

I do see more and more machinery being built in the US in metric, but I am pretty sure the building industry will never go metric here; it is too entrenched.

Interestingly, I have both an Architect's scale, and an Engineer's scale, and the Architect's scale measures feet and inches, and the Engineer's scale measures feet in tenths.

My drawings are normally made using an Engineer's scale, not necessarily an Architect's scale, unless it is a building plan or something, and I am more comfortable with measuring things in decimal than using Architectural nomenclature.

And on a totally unrelated topic, I ran into a Brit who is a member of the local running club.

We have a running series where thousands of people run 10 races total, starting with two 5K's, then two 5 miles, and finally ending with two 1/2 marathons.

We were chatting, and I asked him "Did you run these in GB?", and he said "No, we don't have these in GB".

He was a really nice fellow, and a good runner too. I could never keep up with him.

He was thrilled to be running with so many people; men and women, at 7:00 A.M. every Sunday.
Its a big thing around here.

Edited By PatJ on 09/04/2022 10:43:37

We used to think like that over here, but in the end it doesn't matter, 30mm is a foot and a metre is 3foot 3 inch.

I just wish my 2014 Jeep knew it lives in the world of the big gallon now, the MPG is literally miles off.

Edited By Dave Halford on 09/04/2022 10:42:47

It is annoying to have to own two sets of tools; ie: wrenches, allen wrenches, sockets, etc., since autos are exclusively metric now, but the old engines I work on are definitely not metric.

Makes for a very heavy tool bag.

.

Hi DMB, as has been said, in engineering using meters & mm's are the norm. When I was working and had to cut and make many large fabricated items, having lengths like 5181.6mm was easier to read and mark out than 2.1816M, simple reason is that the thousand unit is full meters and the hundreds, tens and single units can simply be read off directly from the tape measure after the 5M point and you don't have to think about working it all out, and I have had to cut metal to 0.5mm over that sort of length, but not always and anything less the 1mm can often be ignored. As been pointed out, 1M is roughly 40 inch's, so it shouldn't be too hard to covert these to visualize the size of something into feet and inch's.

Regards Nick.

Well it's water, so that's a bit over 3 3/4 cables (Admiralty - Imperial).

Ah - wait, but you're in America, so it's about 3.19 of your cables...

At CAV, because of tghe original licence to manufactire Bosch products under licence, the standard units for measurement were Metric.

But I was involved in developing another product, which being American was to Imperial, and Unified standars.

So we had drawings calling for parts to be 6.354 mm diameter.

So we often worked in both systems, (for odd fixtures, sometimes in both )

And my toolkit included Whitworth spanners as well as A/F and Metric!

In essence, the units are a measurement of an object. The one to use is that which is most convenient.

In photographic film, speeds (sensitivities ) were derived by different methods and so measured in different units  

So there were Hurter and Driffield, Weston, Scheiner, Gost, BS and ASA. film speeds

All applicable to the same material.

Merely a different unit for the same thing.

You will be just as tired after walking 50 Kilometres as if you had walked 30 UK miles

The wood occupies the same space whether it is 8 feet long, or 24438,4 mm long, and you are going to cut bit anyway, in most cases.

You just need to make the raw material large enough that it can made to the required size..

Howard

Hi Howard, or would that be small enough.

Regards Nick.

Yes, Nicholas, no point in wasting good material.

That just inflates the cost and time to produce the end product.

Howard

I know I've posted this before, but it's still worth a re-read of "Which Inch" 6 pages
http://metricationmatters.com/docs/WhichInch.pdf

There's a rather longer treatise here; "A chronological history of the modern metric system (to 2008)" 142 pages
http://www.metricationmatters.com/docs/MetricationTimeline.pdf

Now don't get me started on the volume of a gallon.

Bill

Were you the bloke who parked next to me on that basis last week?

Edited By V8Eng on 09/04/2022 11:54:41

Edited By V8Eng on 09/04/2022 11:59:58

Do not tell the Furniture trade and Estate Agents that!

Very likely it was

I still refer to pairs (prs) of hinges or 1 1/2 prs, 2 pair (s), and so on. Was /is standard in the building industry.....when I was young! Hinges come and fit in twos well nearly! So contract could have say 200++++prs (400+++) + of hinges, etc. Were sold in pairs, so a half pair = one.

My introduction to metric was my first technical exam,.........I was told by a lecturer......'its easy, remember one inch equals 25.4 mm'........... as I walked through the door of the exam room. I passed but questioned every exam thereafter! I also remember not being handed out log tables, formulas, and other hand outs as part of the info made available. I questioned the adjudicator (all listed on the exam paper) and was told.....' its too late you will just have to get on'.....a riot arose the exam room....panic for adjudicator. Passed it but it would have meant a complete failure and the sack from work.

Just shows the standard of the adjudicators and they couldn't sitting the exam. Happy days...no it wasn't. Best wishes to all.

Completely correct, we haven't built anything here in Europe since the French Revolution. Every we time we start digging a foundation we get confused and have to go on strike.

When dimensioning a convex or concave curved profile on a component, radius is certainly a legitimate engineering definition. When I was a tooling designer I'd use it freely in drawings whenever appropriate, as did every other designer whose work I ever saw.